This application is based on Japanese Patent Application Nos. 10-363352 (1998) filed Dec. 21, 1998 and 11-355069 (1999) filed Dec. 14, 1999, the contents of which are incorporated hereinto by reference.
1. Field of the Invention
The present invention relates to a recording apparatus and a method for adjusting a recording position. More particularly, for instance, the present invention relates to recording position corrections in a serial printer carried out if images are recorded on a recording medium by means of both main scanning in a forward direction of a recording head and main scanning in a reverse direction thereof, or to recording position corrections among a plurality of recording heads carried out if these heads are used for recording.
2. Description of the Related Art
In general, a serial printer includes a recording head mounted therein for reciprocating movement in a main scanning direction of a recording medium. In bi-directional recording in which images are recorded during both a forward and a reverse movements of the head, if, for example, an image portion formed during main scanning in the forward direction and an image portion formed during main scanning in the reverse direction are forced to be continuous in a feeding (sub-scanning) direction of the recording medium, and if a recording position obtained by main scanning in the reverse direction is offset from a recording position obtained by main scanning in the forward direction, the image portions will be discontinuous in the feeding direction of the recording medium. Thus, it is strongly desirable to correct the offset of the recording position between the forward and reverse directions of main scanning beforehand. Hereinafter, this correction is referred to as a bi-directional recording-position correction. The causes of the offset of the recording position during bi-directional recording include a backlash in a gear or a timing belt for transmitting a driving force to reciprocate, in the main scanning direction, a carriage with the recording head mounted thereon.
Conventional bi-directional recording-position correction methods include an automatic bi-directional correction of the recording position based on operations of the carriage. Such a method provides means for detecting the recording position relative to the movement of the carriage in order to detect a difference between the actual movement in the forward direction and the actual movement in the reverse direction when the carriage is driven in the forward and reverse directions by the same amount, thereby adjusting the amount by which the carriage is driven, in the forward and reverse directions. In addition, some of the methods record a plurality of sample images with different recording timings during the forward and reverse movements so that a user can determine an optimal correction amount from these sample images.
In addition, due to the recent trend to record images in colors, some serial printers include a plurality of recording heads on the same carriage or different carriages, which have individual enclosures for ejecting a plurality of color inks. In this case, the plurality of recording heads are separate, so when they are mounted on the carriages, each recording head is likely to be misaligned from its ideal mounting position in the main scanning direction and sub-scanning direction due to the dimensional accuracy of the recording head or the accuracy with which the head is mounted. With this offset of each recording head from the ideal mounting position, a position on a recording medium at which each color image is recorded by each recording head may be offset from its theoretical position, thereby changing the hue (color reproducibility) of recorded images. Thus, it is strongly desirable to appropriately correct the recording position in the main scanning direction (a carriage moving direction) and sub-scanning direction (a paper feeding direction) at which each image (each color) is recorded by each recording head, despite the offset of each recording head from the ideal mounting position. For such corrections, conventional methods record on a recording medium a plurality of sample images obtained using different recording timings for each recording head so that a user can determine an optical correction amount based on a result obtained from the sample images.
However, in reciprocating main scanning for bi-directional recording or recording in the main scanning direction and sub-scanning direction using a plurality of heads, the method for correcting the recording position by essentially recording a plurality of sample images so as to select an optimal correction amount based on a result obtained from the sample images casts a heavy burden on a user and is insufficiently reliable. In addition, in reciprocating main scanning for bi-directional recording, the method for automatically and indirectly correcting the recording position based on the difference in carriage movement between the two directions does not correct actual errors in the recording position in the two directions, so this method may result in inaccurate bi-directional corrections.
In view of the above problems, it is thus an object of the present invention to automatically and accurately correct the recording position if images are recorded on a recording medium by means of both main scanning in the forward direction of the recording head and main scanning in the reverse direction thereof, while similarly correcting the recording position among a plurality of recording heads if these heads are used for recording.
In the first aspect of the invention, there is provided a recording apparatus for forming an image by means of main scannings as a reciprocating operation of a recording head and sub-scanning as a relative moving operation between the recording head and a recording medium in a direction different from the main scanning direction, comprising:
image formation means for forming predetermined images at predetermined positions on the recording medium during the forward direction main scanning and reverse direction main scanning of the recording head;
image detection means for performing main scanning on the recording medium to detect the predetermined images formed during the forward direction main scanning and reverse direction main scanning;
measuring means for measuring the interval between the predetermined images formed during the forward direction main scanning and reverse direction main scanning, based on output from the image detection means; and
data processing means for calculating the amount of offset between the recording position of the image formed during the forward direction main scanning and the recording position of the image formed during the reverse direction main scanning, based on measurements carried out by the measuring means.
In the second aspect of the invention, there is provided a recording position correcting method with respect to a recording apparatus for forming an image by means of main scannings as a reciprocating operation of a recording head and sub-scanning as a relative moving operation between the recording head and a recording medium in a direction different from the main scanning direction, the method comprising the steps of:
forming predetermined images at predetermined positions on the recording medium during the forward direction main scanning and reverse direction main scanning of the recording head;
detecting the predetermined images formed during the forward direction main scanning and reverse direction main scanning, by using image detection means being main scanning on the recording medium;
measuring the interval between the predetermined images formed during the forward direction main scanning and reverse direction main scanning, based on output from the image detection means; and
calculating the amount of offset between the recording position of the image formed during the forward direction main scanning and the recording position of the image formed during the reverse direction main scanning, based on measurements carried out by the measuring step.
In any of these aspects, the image formation means or step may form a reference image at a predetermined position on the recording medium during the forward direction main scanning of the recording head, the reference image extending in the sub-scanning direction, while forming particular images at the predetermined position on the recording medium during the forward direction main scanning and reverse direction scanning of the recording head, the predetermined position being different from that of the reference image;
the image detection means or step may perform main scanning on the recording medium to detect the reference image and the particular images formed during the forward direction main scanning and reverse direction main scanning; and
the measuring means or step may measure the image interval in the main scanning direction between the reference image and each of the particular images formed during each of the forward direction main scanning and reverse direction main scanning, based on an output from the image detection means.
The image detection means or step may use a sensor placed on a carriage for allowing the recording head to carry out main scanning in the forward and reverse directions.
The measuring means or step may use means for generating a reference clock and means for measuring the interval by counting the reference clock between a point of time at which the image detection means detects, through main scanning, the particular image formed during the forward direction main scanning and a point of time at which the image detection means detecting the reference image through main scanning and between a point of time at which the image detection means detects, through main scanning, the particular image formed during the reverse direction main scanning and a point of time at which the image detection means detects the reference image through main scanning.
Here, the reference clock generation means may be also used as means for generating a clock for defining recording timings for the recording head.
Further, in the above, the image detection means or step may detect the quantity of reflected light resulting from irradiation of the recording medium with light, and may use a sensor for indicating a change in the quantity of reflected light depending on whether an image may be formed on the recording medium.
Here, the measuring means or step may measure the interval by measuring a time interval at which the quantity of reflected light changes while moving the sensor at a constant speed in the main scanning direction relative to the predetermined image, and multiplying the time interval by the speed.
In the third aspect of the invention, there is provided a recording apparatus for forming an image by means of main scanning executed by a plurality of recording heads and sub-scanning as a relative moving operation between the recording heads and a recording medium in a direction different from the main scanning direction, comprising:
image formation means for forming predetermined images at predetermined positions on the recording medium by using the plurality of recording heads;
image detection means for performing scanning on the recording medium to detect the predetermined images formed by the plurality of recording heads;
measuring means for measuring the interval between the predetermined images formed by the plurality of recording heads, based on output from the image detection means; and
data processing means for calculating the amounts of offset of the recording positions of the images formed by the plurality of recording heads, based on measurements carried out by the measuring means.
In the fourth aspect of the invention, there is provided a recording position correcting method with respect to a recording apparatus for forming an image by means of main scanning executed by a plurality of recording heads and sub-scanning as a relative moving operation between the recording heads and a recording medium in a direction different from the main scanning direction, the method comprising the steps of:
forming predetermined images at predetermined positions on the recording medium by using the plurality of recording heads;
detecting the predetermined images formed by the plurality of recording heads by using image detection means being scanning on the recording medium;
measuring the interval between the predetermined images formed by the plurality of recording heads, based on output from the image detection means; and
calculating the amounts of offset of the recording positions of the images formed by the plurality of recording heads, based on measurements carried out by the measuring step.
In any of the third and fourth aspects, the image formation means may form a reference image at a predetermined position on the recording medium during the forward or reverse direction main scanning of one of the recording heads, the reference image extending in the sub-scanning direction, while forming particular images at predetermined positions on the recording medium in the main scanning direction by the plurality of recording heads, the predetermined positions being different from that of the reference image;
the image detection means may perform main scanning on the recording medium to detect the reference image and the particular images formed by the recording heads; and
the measuring means may measure the interval in the main scanning direction between the reference image and each of the particular images formed by the plurality of recording heads, based on output from the image detection means.
Here, the image detection means may use a sensor placed on one carriage for integrally holding the plurality of recording heads for main scanning or one of a plurality of carriages for individually holding the plurality of recording heads for main scanning.
Further, the measuring means or step may use means for generating a reference clock and means for measuring the interval by counting the reference clock between a point of time at which the image detection means detects, through main scanning, each of the particular image formed by each of the plurality of recording heads and a point of time at which the image detection means detects the reference image through main scanning.
Here, the reference clock generation means may be also used as means for generating a clock for defining recording timings for the recording heads.
Alternatively, in the third and forth aspect, the image formation means or step may form a reference image at a predetermined position on the recording medium during the forward or reverse direction main scanning of one of the recording heads, the reference image extending in the main scanning direction, while forming particular images at predetermined positions on the recording medium in the main scanning direction by using the plurality of recording heads, the predetermined position being different from that of the reference image;
the image detection means or step may perform sub-scanning on the recording medium to detect the reference image and the particular images formed by the recording heads; and
the measuring means or step may measure the interval in the sub-scanning direction between the reference image and each of the particular images formed by each of the plurality of recording heads, based on output from the image detection means.
Here, the image detection means or step may use a sensor placed on one carriage for integrally holding the plurality of recording heads for main scanning or one of a plurality of carriages for individually holding the plurality of recording heads for main scanning, and may set the carriage at a position in the main scanning direction at which the sensor detects the reference image and the particular image during sub-scanning of the recording medium.
The measuring means or step may use means for generating a reference clock and means for measuring the interval by counting the reference clock between a point of time at which the image detection means detects, through sub-scanning, each of the particular image formed by each of the plurality of recording heads and a point of time at which the image detection means detects the reference image through sub-scanning.
Here, the reference clock generation means may be also used as means for generating a clock for defining recording timings for the recording heads.
Further, a drive source for the sub-scanning may perform rotating motions, and the particular image may be formed at a position corresponding to an integral multiple of a travel distance obtained by a single rotation of the drive source.
Moreover, the image detection means or step may detect the quantity of reflected light resulting from irradiation of the recording medium with light, and may use a sensor for indicating a change in the quantity of reflected light depending on whether an image may be formed on the recording medium.
Further, the measuring means or step may measure the interval by measuring a time interval at which the quantity of reflected light changes while moving the sensor at a constant speed relative to the predetermined image, and multiplying the time interval by the speed.
In the fifth aspect of the invention, there is provided a recording apparatus for forming an image by means of main scanning as a reciprocating operation of a recording head and sub-scanning as a relative moving operation between the recording head and a recording medium in a direction different from the main scanning direction, comprising:
image formation means for forming predetermined images at predetermined positions on the recording medium during the forward direction main scanning and reverse direction main scanning of the recording head;
image detection means for performing main scanning on the recording medium to detect the predetermined images formed during the forward direction main scanning and reverse direction main scanning; and
data processing means for determining a center position of the predetermined image in the main scanning direction from detection start and end positions of the predetermined image associated with main scanning by the image detection means, and calculating the amount of offset between the recording position of the predetermined image formed during the forward direction main scanning and the recording position of the predetermined image formed during the reverse direction main scanning, based on the main-scanning direction center positions of the predetermined images formed in the forward direction main scanning and reverse direction main scanning.
In the sixth aspect of the invention, there is provided a recording position correcting method with respect to a recording apparatus for forming an image by means of main scanning as a reciprocating operation of a recording head and sub-scanning as a relative moving operation between the recording head and a recording medium in a direction different from the main scanning direction, the method comprising the steps of:
forming predetermined images at predetermined positions on the recording medium during the forward direction main scanning and reverse direction main scanning of the recording head;
detecting the predetermined images formed during the forward direction main scanning and reverse direction main scanning, by using image detection means being main scanning on the recording medium; and
determining a center position of the predetermined image in the main scanning direction from detection start and end positions of the predetermined image associated with main scanning by the image detection means, and calculating the amount of offset between the recording position of the predetermined image formed during the forward direction main scanning and the recording position of the predetermined image formed during the reverse direction main scanning, based on the main-scanning direction center positions of the predetermined images formed in the forward direction main scanning and reverse direction main scanning.
In any of the fifth and sixth aspects, the image formation means or step may form a reference image at a predetermined position on the recording medium during the forward direction main scanning of the recording head, the reference image extending in the sub-scanning direction, while forming particular images at predetermined positions on the recording medium during the forward direction main scanning and reverse direction scanning of the recording head, the predetermined position being different from that of the reference image;
the image detection means or step may perform main scanning on the recording medium to detect the reference image and the particular images formed during the forward direction main scanning and reverse direction main scanning; and
the data processing means or step may calculate the amount of offset based on the distance between the center position of the particular image formed during the forward direction main scanning and the center position of the reference image, and also based on the distance between the center position of the particular image formed during the reverse direction main scanning and the center position of the reference image.
Further, the image detection means or step may detect the quantity of reflected light resulting from irradiation of the recording medium with light, and may use a sensor for indicating a change in the quantity of reflected light depending on whether an image may be formed on the recording medium.
In the seventh aspect of the invention, there is provided a recording apparatus for forming a image by means of main scanning executed by a plurality of recording heads and sub-scanning as a relative moving operation between the recording heads and a recording medium in a direction different from the main scanning direction, comprising:
image formation means for forming predetermined images at predetermined positions on the recording medium by using the plurality of recording heads;
image detection means for scanning the recording medium to detect the predetermined images formed by the plurality of recording heads; and
data processing means for determining a center position of the predetermined image in a scanning direction of the image detection means, from detection start and end positions of the predetermined image associated with scanning by the image detection means, and calculating the amount of offset between the recording positions of the predetermined images formed by the plurality of recording heads, based on the center positions of the predetermined images formed by the plurality of recording heads.
In the eighth aspect of the invention, there is provided a recording position correcting method with respect to a recording apparatus for forming a image by means of main scanning executed by a plurality of recording heads and sub-scanning as a relative moving operation between the recording heads and a recording medium in a direction different from the main scanning direction, the method comprising the steps of:
forming predetermined images at predetermined positions on the recording medium by using the plurality of recording heads;
detecting the predetermined images formed by the plurality of recording heads image, by using detection means being scanning on the recording medium; and
determining a center position of the predetermined image in a scanning direction of the image detection means, from detection start and end positions of the predetermined image associated with scanning by the image detection means, and calculating the amount of offset between the recording positions of the predetermined images formed by the plurality of recording heads, based on the center positions of the predetermined images formed by the plurality of recording heads.
In any of the seventh and eighth aspects, the image formation means or step may form a reference image at a predetermined position on the recording medium during the forward or reverse direction main scanning of one of the recording heads, the reference image extending in the sub-scanning direction, while forming particular images at predetermined positions on the recording medium in the main scanning direction using each of the plurality of recording heads, the predetermined position being different from that of the reference image;
the image detection means or step may perform main scanning on the recording medium to detect the reference image and the particular images formed by the recording heads; and
the data processing means or step may calculate the amount of offset based on the distance between the center position in the main scanning direction of each of the particular images formed by a corresponding one of the plurality of recording heads and the center position of the reference image in the main scanning direction.
Alternatively, the image formation means or step may form a reference image at a predetermined position on the recording medium during the forward or reverse direction main scanning of one of the recording heads, the reference image extending in the main scanning direction, while forming particular images at predetermined positions on the recording medium in the sub-scanning direction using each of the plurality of recording heads, the predetermined position being different from that of the reference image;
the image detection means or step may perform sub-scanning on the recording medium to detect the reference image and the particular images formed by the recording heads; and
the data processing means or step may calculate the amount of offset based on the distance between the center position in the sub-scanning direction of each of the particular images formed by a corresponding one of the plurality of recording heads and the center position of the reference image in the sub-scanning direction.
In these, the image detection means or step may detect the quantity of reflected light resulting from irradiation of the recording medium with light, and may use a sensor for indicating a change in the quantity of reflected light depending on whether an image may be formed on the recording medium.
In the ninth aspect of the invention, there is provided a recording apparatus for forming an image by allowing one or more recording heads to relatively scan a recording medium, comprising:
image formation means for forming images at predetermined positions on the recording medium by means of a plurality of recording operations performed by the one or more recording heads;
image detection means for detecting the predetermined images formed by each of the plurality of recording operations, the image detection means having a sensor for detecting the quantity of reflected light resulting from irradiation of the recording medium with light and indicating a change in the quantity of reflected light depending on a rate at which an image may be present within the detection range; and
data processing means for setting the sensor at an identical position in the scanning direction in a boundary portion of each of the predetermined images on the recording medium that are formed by each of the plurality of recording operations, in order to detect the quantity of light, and for calculating the amount of offset of the recording positions of the images obtained by the plurality of recording operations based on the difference in the detected amount of reflected light.
In the tenth aspect of the invention, there is provided a recording position correcting method with respect to a recording medium for forming an image by allowing one or more recording heads to relatively scan a recording medium, the method comprising the steps of:
forming images at predetermined positions on the recording medium by means of a plurality of recording operations performed by the one or more recording heads;
detecting the predetermined images formed by each of the plurality of recording operations, by using image detection means having a sensor for detecting the quantity of reflected light resulting from irradiation of the recording medium with light and indicating a change in the quantity of reflected light depending on a rate at which an image may be present within the detection range; and
setting the sensor at an identical position in the scanning direction in a boundary portion of each of the predetermined images on the recording medium that are formed by each of the plurality of recording operations, in order to detect the quantity of light, and calculating the amount of offset of the recording positions of the images obtained by the plurality of recording operations based on the difference in the detected amount of reflected light.
In any of the ninth and tenth aspects, in the boundary portion between a portion of the recording medium with an image formed therein and a portion with no image formed therein, the data processing means or step may move the sensor between at least two positions having different rates at which an image may be present within the detection range, in order to calculate the amounts of offset of the recording positions of the images obtained by the plurality of recording operations, based on the quantities of reflected light at the two positions, the travel distance, and the difference.
The recording apparatus may form an image by means of main scanning as a reciprocating operation of a recording head and sub-scanning as a relative moving operation between the recording head and a recording medium in a direction different from the main scanning direction, the plurality of recording operations being performed in the forward direction main scanning and reverse direction main scanning, wherein;
the image formation means or step may form the predetermined images at a theoretical identical position in the main scanning direction during each of the forward direction main scanning and reverse direction main scanning of the recording head; and
the data processing means or step may set the sensor at an identical position in the main scanning direction in the boundary portion of each of the predetermined images on the recording medium.
Alternatively, the recording apparatus may form an image by means of main scanning executed by a plurality of recording heads and sub-scanning as a relative moving operation between the recording heads and a recording medium in a direction different from the main scanning direction, the plurality of recording operations being performed by main scanning using the plurality of recording heads, wherein
the image formation means or step may form the predetermined image at a theoretical identical position in the main scanning direction by means of each of the plurality of recording heads.
Alternatively, the recording apparatus may form an image by means of main scanning executed by a plurality of recording heads and sub-scanning as a relative moving operation between the recording heads and a recording medium in a direction different from the main scanning direction, the plurality of recording operations being performed by sub-scanning using the plurality of recording heads, wherein
the image formation means or step may form the predetermined image at a theoretical identical position in the sub-scanning direction by means of each of the plurality of recording heads.
In any of the first to tenth aspects, there may be further provided means or step for correcting recording data or timings for recording an image on the recording medium, based on the amount of offset of the recording position determined by the data processing means or step.
The recording head may be a head for performing recording by ejecting ink.
Here, the recording head may have heating elements for generating thermal energy to make the ink to film-boil, as an energy used for ejecting the ink.
Incidentally, hereafter, the word xe2x80x9crecordxe2x80x9d represents not only forming of significant information, such as characters, graphic image or the like but also represent to form image, patterns and the like on the printing medium irrespective whether it is significant or not and whether the formed image elicited to be visually perceptible or not, in broad sense, and further includes the case where the medium is processed.
Here, the wording xe2x80x9crecording mediumxe2x80x9d represents not only paper to typically used in the printing apparatus but also cloth, plastic film, metal plate and the like and any substance which can accept the ink in broad sense.
Furthermore, the wording xe2x80x9cinkxe2x80x9d has to be understood in broad sense similarly to the definition of xe2x80x9cprintxe2x80x9d and should include any liquid to be used for formation of image patterns and the like or for processing of the printing medium.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.